Mursi, an Islamist, is competing against Ahmed Shafiq, who served as prime minister under former President Hosni Mubarak.

Mursi's Muslim Brotherhood said he was holding a 52%-48% lead over Shafiq with almost all the vote counted after Sunday's second-round run-off election.

Speaking at his party headquarters, Mursi pledged to be a president for all Egyptians, adding that he would not "seek revenge or settle scores".

"Thanks be to God who has guided Egypt's people to the path of freedom and democracy, uniting the Egyptians to a better future," he said.

But Shafiq's campaign said it rejected "completely" the victory claim by Mursi.

"We are astonished by this bizarre behaviour which amounts to a hijacking of the election results," Shafiq campaign official Mahmud Barakeh was quoted as saying by the AFP news agency.

Official results have yet to be announced.

The election - the first since Hosni Mubarak was forced from office in 2011 - also comes amid a bitter row over the dissolution of parliament following a court ruling on Thursday.

The Brotherhood has denounced the step as unlawful and a coup against democracy.

The SCAF issued its declaration late on Sunday - just hours after the polls closed.

The document effectively gives the SCAF control over the budget and who writes the permanent constitution following mass street protest that toppled Mubarak, reports say. It also strips the president of any authority over the army.

The full details of the declaration are expected to be announced later on Monday.

However, prominent political leader Mohammed ElBaradei already described the document as a "grave setback for democracy and revolution".

The Brotherhood earlier urged Egyptians to protect their revolution after the SCAF declared the parliament null and void on Saturday.

Two days earlier, the Supreme Constitutional Court ruled that last year's legislative polls were unconstitutional because party members were allowed to contest seats in the lower house reserved for independents.

The decision was made by judges appointed under Mr Mubarak.

The dispute has laid bare the fears of some that the military council is trying to consolidate power and resist the democratic changes demanded during last year's demonstrations.

Soldiers have already been stationed around the parliament with orders not to let MPs enter.

Pro-revolutionary groups meanwhile say they will stage a protest in Cairo's Tahrir Square on Sunday night to keep up the pressure for reforms. Law and order

Polls began closing at 22:00 (20:00 GMT), after voting was extended by two hours.

Turnout appeared to be down compared to the first round.

The BBC's Jon Leyne says that there is less enthusiasm in the run-off election than there was for previous rounds of voting, and some have called for a boycott or spoiled ballots.

Many voters have expressed scepticism at the choices they face, and have voted with reluctance.

"Boycotting the elections is not a practical solution because at this point one of the two candidates will win anyway," Saber Abdullah, voting in Alexandria, told the BBC.

"I demand the next president to concentrate on helping the youth because the old regime have ignored them to the extent that they have reached rock bottom."

Shafiq has campaigned on a platform of a return to stability and law-and-order which, correspondents say, many find attractive after months of political turmoil.

But to his critics, the former air force officer is the army's unofficial candidate and a symbol of the autocratic days under Mubarak.

Mursi, meanwhile, has cast himself as a revolutionary and part of the movement that overthrew Mubarak, and has promised economic and political reform.